The present invention relates to a veneer core block for plywood and particularly to green veneer plates or strips, which have been formed by cutting a thin wood sheet to a maximum effective width by means of a veneer lathe, a veneer slicer, etc., for a veneer core block used for plywood. The present invention also relates to a method for forming a veneer core block and more particularly to method for connecting or linking green veneer strips side by side to form a veneer core block for plywood.
Many kinds of plywood have been provided hitherto having desired rigidity, hardness, or strength. Among these known plywoods, there has recently been provided a rigid plywood which comprises a veneer core block having a number of thin and narrow wood strips adhered side by side with their grains in the same direction, and relatively wide backing plates attached to the upper andlower surfaces of the veneer core block. In order to form plywood of this type, a number of wood strips are cut out of a thin wood sheet with a maximum effective width and the cut-out wood strips are arranged side by side and then adhered in a close contact with each other.
Generally, veneer core blocks for plywood have been formed by sewing green veneer strips which are closely contacted as described above or by affixing an adhesive tape on the surface of the closely contacted green veneer strips. In another method which has generally been applied, the veneer core blocks have been formed by providing a suitable adhesive agent on the entire surface of the opposing sides of the closely contacted green veneer strips, thereby establishing a side-by-side connection or linking of the green veneer strips to form a veneer core block for plywood.
However, it has been found that the conventional methods in which the green veneer strips are connected by strings or adhesive tapes produced such disadvantages that the methods lack efficiency and the connection of the green veneer strips is unstable. Further, the strings and adhesive tapes used for connecting the green veneer strips have been found to be objectionable particularly when thin wood backing sheets are adhered to the upper and lower surfaces of the connected green veneer strips for forming the desired plywood since the strings and tapes are exposed on the surfaces of the veneer strips and produce an objectionable uneveness or roughness on the surfaces thereof.
In the conventional method in which a desired adhesive agent is applied to the opposing sides of the green veneer strips which are in a close contact with each other, it has been found that the adhesive agent is often forced out of the surfaces of the green veneer strips and comes out from between the closely contacted sides of the veneer strips to result in an objectionable adhesion or connection with upper and lower green veneer strips when the green veneer strips are piled after the connection operation is finished. In order to overcome this objection, an attempt has been made in which sheets made of polyethylene or the like are inserted between the layers of the piled green veneer strips, i.e., veneer core blocks, to prevent the undesired adhesion between the upper and lower veneer core blocks. However, it has been found that this is time-consuming, troublesome and expensive, and requires complex steps.
Accordingly, an object of the present invention is to provide a veneer core block for plywood wherein a stable connection of green veneer strips is accomplished.
Another object of the present invention is to provide an economical veneer core block for plywood wherein a simple operation allows production of the core block.
A further object of the present invention is to provide a veneer core block for plywood wherein the core block has smooth surfaces.
Another object of the present invention is to provide a new method for forming a veneer core block for plywood.
Another object of the present invention is to provide a method which makes it possible to form a veneer core block for plywood efficiently and economically.
A further object of the present invention is to provide a method for forming a veneer core block which has smooth upper and lower surfaces.